Directly cooled circuit board for an electronic power circuit

ABSTRACT

In order to improve the cooling of one sided circuit boards for electronic power circuits in SMD configuration, the surface (14) of the circuit board (10) which is not provided with circuit components is part of the interior wall of a housing (26) through which flows a liquid coolant and which is equipped with inlet and outlet pipe connections (28, 30) for conduits through which flows a coolant. In order to remove heat, the side (14) of the circuit board (10) which is not provided with the circuit components can be directly wetted with coolant.

BACKGROUND OF THE INVENTION

The invention relates to a one sided circuit board for an electronicpower circuit in SMD (surface mounted device) configuration.

Prior art circuit boards for electronic power circuits of this type areconfigured so that, in order to dissipate the resulting heat, either theentire circuit board or all circuit components involved in thedevelopment of excessive heat are mounted on cooling bodies. If powerconsumption is high, for example 250 W and more, such circuit boardsand/or the cooling bodies must additionally be cooled by means of a fan.As a whole, this undesirably increases the structural volume requiredfor such electronic power circuits.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to provide a circuit boardfor an electronic power circuit in SMD configuration which, whileavoiding the above-mentioned drawbacks, ensures sufficient good coolingin spite of its small structural configuration even with high powerconsumption.

The above object generally is accomplished according to the invention bya novel arrangement of a one-sided circuit board for an electronic powercircuit in SMD configuration. More particularly, the above object isachieved according to the present invention by an arrangement whichcomprises a circuit board having first and second opposed surfacesformed of one of a steel substrate and a ceramic material substrate, anelectronic power circuit in a surface mounted device configurationdisposed on only the first surface of the circuit board, and a housingthrough which a liquid coolant flows which is and which is provided withinlet and outlet pipe connections for a liquid coolant, with the secondsurface of the circuit board forming at least a portion of an interiorsurface of a wall of the housing.

The integration, according to the invention, of the circuit board itselfin a housing through which flows a liquid coolant brings about the greatadvantage of permitting simple and possibly even pressure-free liquidcooling of the circuit board. In particular, if the circuit boardaccording to the invention is employed in machines which are equippedwith a liquid circulating system, for example washing machines (watersupply), ultrasonic washers and automobiles (radiator circulation), thecircuit board according to the invention can be very easily integratedin the path of the circulating liquid as the cover of an alreadyexisting housing. In such cases, the additional space requirement, ifany, for the circuit board according to the invention is very little,particularly when compared to the cooling bodies and/or fans required inthe past.

As an advantageous feature of the invention, it is further provided thatthe circuit board according to the invention is configured in the formof a known hybrid board so that a very high mechanical strength can berealized for the circuit board and it can be adapted in this way, aspart of a housing through which a coolant flows, to the mechanicalstrengths applicable for the housing.

Such a circuit board according to the invention in hybrid configurationcan be manufactured in almost all conceivable shapes by means of knownmanufacturing processes and can be employed in the form of a cover or ina similar way on almost any housing shape, for example on rectangular,box-shaped, tubular or triangular housings or on shapes derivedtherefrom.

As a particular feature of the invention it is further provided that afurther circuit for monitoring and determining its temperature and forcontrolling and regulating the coolant stream is provided on the circuitboard according to the invention in addition to the electronic powercircuit. In this way, it is possible in a simple manner to regulate andadapt the flow of coolant, as a function of the power consumption andthe heat inevitably developed thereby, to the amount of heat necessaryto be removed.

Further advantageous features of the invention are defined in thedependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below and explained in detail withreference to the drawings wherein:

FIG. 1 is a schematic plan view of an embodiment of a circuit boardaccording to the invention;

FIG. 2 is a side view of a rectangular, box-shaped housing including acircuit board according to FIG. 1 as the cover;

FIG. 3 is a sectional view of the housing of FIG. 2 seen approximatelyat the level of the marking indicated as III--III in that figure;

FIG. 4 shows a housing having a triangular cross section and equippedwith a circuit board according to FIG. 1 as cover; and

FIG. 5 shows a tubular housing including a circuit board according toFIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the embodiment of a unilaterally equipped i.e., one-sidedcircuit board 10 according to the invention which includes an electronicpower circuit 16 and a further circuit 18 for determining and monitoringthe circuit board temperature (and for determining the temperature of acoolant) and for controlling subsequently connected adjustment members.As shown, the circuits 16 and 18 are connected via printed circuit paths20 to a connector 22.

The electronic configuration of such circuits 16, 18 is familiar to theperson skilled in the art; they are configured in a known manner asprinted circuits in SMD configuration. For the sake of simplicity,circuits 16, 18 are therefore shown only schematically.

Due to the SMD configuration and design of circuit board 10 thereresults an equipped or circuit bearing side or surface 12, and anunequipped or non-circuit bearing side or surface 14 of the circuitboard 10, with the latter being possibly exposed directly to the coolantstream.

Preferably, if more strength is required, circuit board 10 ismanufactured as a hybrid card, with circuit board 10 being composed,depending on the intended application, of a metal containing material,for example, a steel substrate provided with a layer of insulatingmaterial on the surface 12 or of a ceramic material.

In order to releasably fasten circuit board 10, screws are provided inthe embodiment shown here whose position on circuit board 10 isindicated by the screw center points marked 24. Of course, other ways offastening circuit board 10 are also conceivable without limiting thescope of the invention, including non-removable types of fastening, suchas, for example, by gluing.

FIG. 2 shows a rectangular, box-shaped housing 26 through which flows aliquid coolant and in which the inventive circuit board 10 of FIG. 1 isused as the cover of a long side or part thereof. The liquid coolant,not shown in detail here, for example water or oil, enters housing 26through an inlet pipe connection marked 28, circulates within housing 26and leaves housing 26 through an outlet pipe connection marked 30. Inorder to impart better turbulence to the coolant within housing 26,inlet pipe connection 28 is preferably configured, as shown in FIG. 2,as an elongate tube that extends into housing 26. Circuit board 10, ofwhich again only the equipped side 12 is visible in FIG. 2, isreleasably connected with housing 26, for example by means of screws 24.The coolant flows directly against the unequipped side 14 of the circuitboard. Of course, without limiting the scope of the invention, bafflewebs or guide zones for changing the direction of flow of the coolantmay also be provided in housing 26 itself in order to improve turbulencein the coolant.

To set the desired quantity of coolant flowing through the box-shapedhousing 26, a flow quantity regulator 34, preferably an electricallyadjustable flow quantity regulator, is provided between the inlet pipe28 and a coolant conduit 32. By way of connections, not shown in detailhere, this flow quantity regulator 34 may be electrically actuated by atemperature determination and monitoring circuit 18 provided on circuitboard 10 (see FIG. 1 in this connection).

Such electrically controllable flow quantity regulators 34 are known tothe person skilled in the art and are not part of the invention. Withoutlimiting the invention it is also conceivable to effect the actualtemperature determination and monitoring by way of a suitably configuredtemperature sensor within housing 26 and to limit temperaturedetermination and monitoring circuit 18 (see FIG. 1) to a purelycomparison and control function.

FIG. 3 is a sectional view of the box-shaped housing 26 of FIG. 2approximately at the height of the line marked III--III in FIG. 2.Maintaining the above-mentioned reference numerals, the illustratedindividual components in their association serve to clarify theattachment and function of the circuit board 10 according to theinvention. Clearly visible in FIG. 3 is the actual circuit board 10 andits unequipped side 14 against which flows, as a result of turbulenceformation, the liquid coolant that has entered into housing 26 throughinlet pipe connection 28.

If circuit board 10 is made of a corrosion sensitive, metal containingmaterial, its unequipped side 14 is preferably provided with a thincorrosion protection coating.

As already mentioned, circuit board 10 is fastened in or to housing 26by means of screws 24 so that it is easy to exchange circuit board 10.Of course, a known seal, for example, a continuous O-ring in anappropriate groove, is provided between circuit board 10 and acontinuous collar, here not identified in detail, of housing 26 on whichcircuit board 10 rests.

FIG. 4 shows a further hollow housing 36 which has an essentiallytriangular cross section and in which, corresponding to the box-shapedhousing 26 shown in FIG. 2, the circuit board 10 according to theinvention is employed as the cover on one long side. Circuit board 10,of which here again only the equipped side 12 is visible, is againconnected with housing 36, for the sake of simplicity, by means ofscrews 24. As another feature of the invention, the inlet pipeconnection 28 for the liquid coolant in the housing shown in FIG. 4 isdisposed in the one end face and the outlet pipe connection 30 isdisposed in the opposite end of the housing 36. Preferably, inlet pipeconnection 28 and outlet pipe connection 30 are not arranged so as to beaxially aligned with one another. In that way, both pipe connections 28,30 can open into the interior of housing 36, individually--as shown inFIG. 2 for the example of inlet pipe connection 28--as extended tubes.As in FIG. 2, this measure serves to provide better turbulence for theliquid coolant within housing 36.

Additionally, the statements made above for housing 26 (FIGS. 2 and 3)apply accordingly here.

To further illustrate the many possible uses for the circuit board 10according to the invention, FIG. 5 shows an essentially closed-endtubular housing 38 provided with an inlet pipe connection 28 and anoutlet pipe connection 30 in its respective opposite end surfaces andwherein circuit board 10 covers and seals a correspondingly configuredrecess, not identified in detail here, in the wall of housing 38. Forthis embodiment of FIG. 5 as well, the statements made above inconnection with the description of FIGS. 1 to 4 apply accordingly.

In practical tests it has already been found that the circuit boardaccording to the invention can be easily integrated as part of a housingof any desired configuration in an existing circulating system for aliquid employed as coolant regardless of the shape of the housing. Theinvention is distinguished by economical manufacture, small structure,low weight and easy installation. Moreover, the invention can beemployed together with economical, commercially available housings whichcan be easily integrated in existing coolant circuits or, if the circuitboard is given a special configuration, the invention can replace coversor corresponding components of housings or parts thereof existing withinthe circulating system.

I claim:
 1. An arrangement comprising: a circuit board having a firstcircuit bearing surface and a second opposed non-circuit bearing surfaceformed of one of a steel and a ceramic substrate having a good thermalconductivity; an electronic power circuit in a surface mounted deviceconfiguration disposed on only said first surface of said circuit board;and a housing having an interior through which a liquid coolant flowsand being provided with inlet and outlet pipe connections for a liquidcoolant, with said second surface of said circuit board forming at leasta portion of an interior surface of a wall of said housing which isdirectly contacted by flowing liquid coolant.
 2. An arrangementaccording to claim 1 wherein said circuit board comprises a steelsubstrate.
 3. The arrangement according to claim 1 wherein the circuitboard is formed of a ceramic material.
 4. The arrangement according toclaim 1 wherein the circuit board is the cover of an essentiallyrectangular, box-shaped housing.
 5. The arrangement according to claim 1wherein the circuit board is the cover of a housing having anessentially triangular cross section.
 6. The arrangement according toclaim 1 wherein the circuit board is the cover of a housing having anessentially tubular cross section.
 7. The arrangement according to claim2, wherein said second surface of the circuit board is provided with acorrosion protection coating.
 8. The arrangement according to claim 1wherein, in addition to the electronic power circuit, said first surfaceof the circuit board is provided with a further circuit for monitoringand determining the temperature of the circuit board and for controllingmeans for regulating the flow of liquid coolant through the housing.